Figuring out positions within a distance between two points.

I haven't tested the following script, but I think it's a good start:

 public Vector3[] GetCollectablePositions( Vector3 pointA, Vector3 pointB, float distance )
 {
     // The direction vector between A and B
     Vector3 direction = pointB - pointA ;
 
     // Get the number of collectables
     int collectableCount = Mathf.Floor( (direction.magnitude - Mathf.Epsilon )  / distance ) ;
 
     // Create the array of positions to gather all the positions
     Vector3[] collectablePositions = new Vector3[collectableCount];
 
     // Direction is now a vector separating two collectables
     direction /= collectableCount ;
 
     // Fill the array by determining the positions of the collectables according to the direction vector
     // and the position of A
     for( int collectableIndex = 0 ; collectableIndex < collectableCount ; ++collectableIndex )
     {
         collectablePositions[collectableIndex] = pointA + direction * (collectableIndex + 1)  ;
     }    
 
     return collectablePositions ;
 }